Self-checkout systems have been previously described and implemented which provide customers with scanners to track their purchasing in stores. Examples of such systems are described in Dutch Patent Application No. 9002296 ("the '296 Application") and U.S. Pat. No. 5,468,942 to Oosterveen et al. ("the Oosterveen Patent"). The '296 Application and the Oosterveen Patent describe systems in which authorized customers are issued a terminal having an integrated bar code scanner to record merchandise purchases. The scanners maintain a list of merchandise selected for purchase by the customer within internal memory means. Prior to exiting the store, the information stored in the memory of the scanner is downloaded through a communication port attached to a terminal dispenser, and a printed receipt of the customer's purchases is printed on a printer. The customer then proceeds to a checkout register where the customer tenders payment for the purchased merchandise. The systems may provide for the occasional audit of customers using the system to ensure integrity of the self-service system.